Rear end growling. About to rebuild all I can reach. Need gears.

[FinallyGot1]

Hello all! There's a disturbing growling coming from the rear end of my '68 Newport. It doesn't seem to change much with throttle setting or speed and is still there when coasting in neutral. I suspect axle bearing(s). So here's my plan: Rebuild the rear end with new axle bearings and any seals I run into. While I'm in there, I thought I'd throw in a TrueTrac differential and a set of 2.75 gears. (What can I say? I like my girls with long legs.) I've been unable to find gears anywhere near that tall for my 8 3/4" rear end though so any help on this would be much appreciated. Already tried Summit, JEGS, and any number of miscellaneous sites and no joy. 3.23 is the best I've been able to do.
Should I also consider replacing U-joints while I'm under there?
I'm trying to get the driveline prepped for a stout motor in the (hopefully) not-too-distant future and I am much more interested in keeping my revs down while cruising the highways than laying rubber from a stoplight.
So. Any thoughts, info, or advice you care to share would be much appreciated.

TIA,
Jason

 

[jake]

I would change out the u-joints, cheap insurance. Why not just go with an open, does not seem like you care if there is traction off the line.

 

[1966newport]

u most likely have 2.76 gears now

 

[FinallyGot1]

I would change out the u-joints, cheap insurance. Why not just go with an open, does not seem like you care if there is traction off the line.

More/better traction is always better IMHO. Besides, it just makes sense to me to upgrade as much as I can while I'm in there.

 

[FinallyGot1]

u most likely have 2.76 gears now

Was thinking I'd need to replace with new when changing the diff but if the gears appear okay then maybe I'll just keep 'em.

 

[commando1]

Rarely have I seen the original ring a/o pinion wear out under normal conditions. Always the bearings a/o seals.

 

[BIGBARNEYCARS]

I replaced ah 323 sure grip with a 276 open That Murray supplied me with ah couple yearz ago. When I went down to Tiffin to pick it up, it turnz out to be a 274????????? An Imperial piece the lived itz whole life in ah '68 300, That'z Mother for yeah, aye? Dropped 500 RPMs @75MPH but the MPG stayed 'tween 8-10 an I lost the ability for 100 yard hole shotz

 

[bulldogchesty]

I changed my 8 3/4 from 2.76 to 3.23 and love it. I still have the 2.76's. Do you have the 489 or 742 pumpkin.

 

[BIGBARNEYCARS]

I have - Had the 879 pumpkin. Sold the 323 SG pig to ah friend that has now gone to live with the Lord. And the 277 open pig installed in the Batwagon haz gone to live with ah new caretaker az of late September last fall

 

[68plymouth383]

You need to find out which case you have. It's ether 741, or 742. Unless someone changed it. Then it could also be a 489 case. The growl is most likely your axle shaft bearings.

 

[commando1]

I replaced ah 323 sure grip with a 276 open That Murray supplied me with ah couple yearz ago. When I went down to Tiffin to pick it up, it turnz out to be a 274????????? An Imperial piece the lived itz whole life in ah '68 300, That'z Mother for yeah, aye? Dropped 500 RPMs @75MPH but the MPG stayed 'tween 8-10 an I lost the ability for 100 yard hole shotz

Sighhh. You kids...

 

[FinallyGot1]

You need to find out which case you have. It's ether 741, or 742. Unless someone changed it. Then it could also be a 489 case. The growl is most likely your axle shaft bearings.

I have the 742. What I don't know is whether I have 30- or 33-spline axles. I need to know so I can order the correct TrueTrac part before everything's taken apart. I'm having a mechanic do the job for me since I have no room to do the work meself and I'd really like him to have the right part to work with.

Any idea how to tell what I've got or which is most likely?